Virus alert: Netsky and MyDoom get updates

New variants of old viruses are causing headaches for computer users this week. Both MyDoom and Netsky have been altered to continue assaulting vulnerable users.

Despite requiring the computer user to actively run an attachment, Netsky.C seems to be spreading fast, with anti-virus vendor Central Command claiming it had discovered 1,500 infections of the virus within 40 minutes of its discovery. Like Netsky.B the latest virus uses its own SMTP engine to email itself to addresses found on the computer, and copies itself into any folder it finds whose name includes "shar".

UK security company mi2g estimated the economic damage done by Netsky.B worldwide to be at least $3.12bn. This was calculated "on the basis of helpdesk support costs, overtime payments, contingency outsourcing, loss of business, bandwidth clogging, productivity erosion, management time reallocation, cost of recovery and software upgrades".

MyDoom.F is the latest variant of the virus that launched a distributed denial of service (DDoS) attack against the SCO Web site early this month. The latest variant launches a DDoS attack against both www.microsoft.com and www.riaa.com if the infected computer's local system is dated between 17 and 22 of any month. The virus also opens a backdoor which will allow crackers to gain access to the computer.

"We firmly believe denial of service attacks that produce wave after wave of downed websites and infected emails are the new reality in the fight against spam, viruses and worms," said Scott Chasin, email management company MX Logic's chief technology officer. "Just consider the number of broadband PCs, sitting on desks, without updated defences and with 'always on' broadband connections - and you immediately understand the opportunity for these assaults."

MyDoom.F also randomly deletes files on the infected computer, a feature that has started to die out from viruses.

James Pearce writes for ZDNet Australia. For more news from ZDNet Australia click here